1. Field of the Invention
This invention relates to a novel organic compound and more particularly to a novel organic compound usable as a component of liquid crystal compositions having a positive value of dielectric anisotropy.
2. Description of the Prior Art
Display elements using liquid crystals utilize the optical anisotropy and dielectric anisotropy of liquid-crystalline substances, and liquid-crystalline phases include nematic phase, smectic phase and cholesteric phase. Currently, display elements using nematic liquid crystals among those of the above phases have most widely been practically used. Such display elements include those of the TN type, DS type, guest-host type, etc., and properties required for liquid crystal compounds used for those of the respective types vary.
Anyhow, as for liquid crystal compounds used for these display elements, there are preferable those which exhibit the liquid-crystalline phase in a temperature range as broad as possible, and also they have been required to be stable to moisture, light, heat, air, etc.
Now, however, there is no single substance which satisfies such conditions; hence it is the present status that several kinds of liquid crystal compounds are employed and if required, non-crystalline compounds have been admixed for practical use.
U.S. Pat. No. 4,198,312 discloses compounds expressed by the formula ##STR3## wherein R.sup.1 represents an alkyl group of 1.about.9 carbons, and U.S. Pat. No. 4,452,719 discloses compounds expressed by the formula ##STR4## wherein R.sup.2 represents an alkyl group of 1.about.10 carbons. However, the compounds of the formula (A) exhibit no liquid-crystalline phase and have high viscosities; hence when used for liquid crystal materials, they have a drawback of narrowing the mesomorphic range of the resulting liquid crystal composition. Further, the compounds of the formula (B) have relatively narrow mesomorphic ranges and relatively high viscosities; hence there is a certain extent of drawback for using them as a component of liquid crystal compositions.